I’d not heard of this before.
I don’t find I have any eye strain at all using dark mode. In principle, your eyes are moving and focusing on the same things. The advantage of dark mode is that it’s not super bright, which I find actually easier on my eyes at night. Plus, it consumes less power from a display device on battery mode.
Just a quick Google search shows this isn’t necessarily an ironed-out thing. Both types of displays can have challenges, depending on a person’s eye conditions.
Summary: In people with normal vision (or corrected-to-normal vision), visual performance tends to be better with light mode, whereas some people with cataract and related disorders may perform better with dark mode. On the flip side, long-term reading in light mode may be associated with myopia.
The human pupil is the gateway to the retina: through it, light reaches the eye. By default, the human pupil changes size depending on the amount of light in the environment: when there is a lot of light, it contracts and becomes narrower, and when it’s dark, it dilates to allow more light to get in.
When researchers looked at fatigue metrics, they concluded that there was no significant difference of contrast polarity on any of them (meaning that it wasn’t the case that dark mode made people more tired, or vice versa).
The study found that lighting, polarity, and text size all had an effect on performance — in the direction perhaps expected by now: simulated daytime led to faster judgements than simulated nighttime, light mode was better than dark mode, and bigger font was faster than smaller font. The interesting result was the significant interaction between ambient lighting and contrast polarity: during daytime, there was no significant effect of contrast polarity, but during nighttime, light mode led to better performance than dark mode. Moreover, during nighttime it was much harder for people to read small-font text in dark mode than in light mode.
An intriguing study published in Nature Research’s Scientific Reports in 2018 suggests that sustained exposure to light-mode may be associated with myopia. Myopia (or nearsightedness) refers to the inability to see far objects clearly and is strongly correlated with the level of education and with reading. In their study, Andrea Aleman and her colleagues at the University of Tübingen in Germany asked 7 human participants to read text presented in dark mode and light mode for an hour each. To see if their predisposition to myopia changed after reading, they measured the thickness of the choroid, a vascular membrane behind the retina. The thinning of the choroid is associated with myopia.x
A WIRED article, HERE, says Dark Mode is not all it’s cracked up to be and may actually be worse… but, it’s a “pop-science” magazine and isn’t known for it’s definitive medically oriented accuracy.
In reality, I use mixed modes across apps and devices. For example, while I use dark mode on Reddit, there’s only light mode on Knockology. My eyes adjust. If it’s too bright, I just tone down the brightness control. My Kindle Paperwhite is light mode only, but it has a phenomenal brightness and tint control. I can easily read it in very dim light.
From all I’ve read, the greatest problem with using these devices is focusing too much on them without a break… which can induce myopia over time. It’s important to break away at least every 30 minutes and focus on long range viewing outside, if you can.